Electric power cable



Allg- 14, 1934 c. E. BENNETT 1,969,720

ELECTRIC POWER-CABLE Filed` Dec 2l, 1932 mg'l/Eok. t

Patented Aug. 14, 1934 UNITED STATES PATENT OFFICE ELECTRIC POWER CABLE Charles E. Bennett, Hawthorne, N. J., assignor to The Okonite-Callender Cable Company, In-

corporated, Paterson, N. J., a

New Jersey corporation of This invention is directed to an improvement in electric cables and is primarily directed to cables in which the oil or other insulating iluid employed is maintained under suflicient pressure to increase the dielectric strength of the insulating uid of the cable, the use of such pressures also reducing the formation of voids and gas pockets to a minimum, all of these improved conlditions greatly improving cable operating conditions. A cable'of the pressure type constitutes the4 subject matter of my copending" application Serial No. 553,714, led July 29, 1931.

One of the objects of my invention is the provision of an improved method for making cables in which I provide a sheath, casing or enclosure for the insulated conductor or conductors of such a nature that when oilo or other insulating fluid is introduced into the cable under pressure, this sheath or casing will expand materially to provide a reservoir for a substantial body of oil constantly maintained under pressure about and in contact with the insulating envelope of the conductor or conductors of the cable with all the advantages accruing thereto set out above.

In the drawing accompanying this application I have shown two embodiments of my invention:

Figs. l and' 2 being sections through a single conductor cable; and

Figs. 3 and 4 being sections through a three conductor cable of the sector type.

Referring to' the drawing in .detail and first of all to the embodiment of my invention as illustrated in Figs. 1 and 2, 1 designates the conductor of the cable which it will be seen is of the solid stranded type. This conductor is insulated by insulation 2 which may be paper tape, for instance. In the process of making this cable a lead sheath or casing 3 is extruded or otherwise applied about the insulation 2.

About the sheath or lead casing 3 I apply extensible material such as canvas 4, for example, which may be in the form of a tape wound spirally about the sheath 3.v On the outside of the canvas 4 I provide sheath 5 of lead or other suitable metal.

Before the cable is placed in operation the sheath or casing 3 is expanded a predetermined amount to the extent permitted by the canvas 4 or other extensible material employed sov as to leave an annular space or reservoir of uniform cross section designated 6 between the insulating envelope 2 and the inner wall of the sheath or casing 3. This expansion of the sheath 3 may well be accomplished during the impregnating operation, the impregnating vfluid, such as oil,

being introduced under sufficient pressure to cause the sheath or casing 3 to expand to the extent above indicated. This, as above noted, will provide a space o1` reservoir which I have designated 6, between the insulation 2 and the 60 inner wall of the sheath 3, this space functioning as a reservoir for insulating uid such as oil with which it is kept filled, this insulating fluid, it being understood, being kept under high pressure at all times.

The pressure employed may be of the order mentioned in my copending application above referred to, for example ve atmospheres minimum 'up to several hundred pounds maximum. The

advantages of employing pressure on the exterior of the insulating envelope of the cable are fully brought out in my copending application, but it may be Well to mention that this pressure increases the dielectric strength of the impregnating fluid of the cable and prevents the formation of voids and gas pockets in the cable from any cause as for example from expansion and contraction of the insulating fluid due to temlperature changes interiorly and/or exteriorly of the cable.

In Figs. 3 and 4 I show a three conductor cable of the sector type, the conductors being designated 'l and each conductor being insulated by an insulating envelope 8 of oil impregnated paper, for instance. The conductors 7 as in the case of the conductors 1 of Figs. 1 and 2 are of the solid stranded type. These insulated conductors are enclosed by any suitable process in a sheath 9 of extensible but relatively inelastic material such as lead, the sheath 9 having applied to its ex- 90 terior an extensible canvas tape 10, for example, similar to the material 4 of Figs. 1 and 2, an outer sheath 11 of lead or other suitable material being applied about the tape l0.

Oil or other suitable insulating fluid 12 is then introduced into the cable under pressure to expand the sheaths 9 and 11 into truly round cross section as shown in Fig. 4, the canvas or other extensible material 10 which lies intermediate the two sheaths 9 and 11 permitting of this expansion but at the same time preventing expansion to the bursting point.V The uid 12 it will be appreciated is maintained under pressure in the operation of the cable with the attendant advantages mentioned in connection with Figs. 1 and 2.

What I claim isz- 1. In the making -of Aelectric cables, the method which comprises enclosing an insulated conductor in an extensibletubular casing engaging the insulation of the conductor, introducing an extensible fibrous material intermediate said sheaths. and then introducing an insulating uid into the cable and maintaining the same under suiiicient pressure to effect permanent expansion oi' the sheath structure a predetermined amount to provide a reservoir or space of uniform cross section for the insulating fluid between the wall bf the casing and the insulation of the conductor.

3. In the making of electric cables of the multiconductor type, the method which comprises enclosing a plurality of separately insulated conductors in an expansible tubular casing non-circular in cross section and then introducing an insulating fluid into the casing and maintaining the samefunder suiiicient pressure to cause the casing to expand permanently a predetermined amount into a round cross section to provide a reservoir of uniform crpss section i'or the insulating fluid between the wail of the casing and the insulation of the conductors and in which iluid the conductors and their insulation are submerged.

CHARLES E. BENNE'I'I. 

